This invention relates to a method and apparatus for processing photographic material. In particular, the invention relates to improving the flow of solution through the processor.
The processing of photosensitive material such as photographic film involves a series of steps such as developing, bleaching, fixing, washing and drying. In this process, a continuous web of film or cut sheet of film is sequentially conveyed through a series of stations or tanks, with each one containing a different processing solution appropriate to the process step at that station.
A large photofinishing apparatus utilizes rack and tank configurations. Such an apparatus is disclosed in, for example, U.S. Pat. No. 5,980,130. This document discloses a rack for use in a low volume thin tank of a photographic processing apparatus. The rack is placed in a processing tank, defining a relatively narrow processing channel between the walls of the tank and the rack. U.S. Pat. No. 5,420,658 discloses a further low volume photographic material processing apparatus which utilizes a narrow substantially horizontal processing channel. The channel has an upturned entrance and exit to contain the processing solution within the channel.
In some conventional small low volume processors the processing solution is returned to the suction input of the circulation pump by allowing it to flow over a barrier at the ends of the processing track. This can lead to air entrainment which can oxidize the chemicals in the solution. Also the solution and aerated solution is returned to the processing chamber to process the film through jets. The position of the jets in relation to the film is not constant. This can give rise to process density variations.
The present invention aims to overcome the problems mentioned above.
According to the present invention there is provide a method of processing photographic material comprising the steps of; feeding the photographic material into a processing channel having an inlet and an outlet; circulating processing solution through the channel such that the solution enters the channel at solution inlets located towards the inlet and the outlet of the channel and exits at a solution outlet located between the inlet and the outlet of the channel, the flow of solution pulling the material down to a fixed position against the surface wall of the channel, and withdrawing the material from the channel once processing is complete.
The invention further provides an apparatus for processing photographic material, the apparatus comprising a module having an upper section and a lower section together defining a processing channel having an inlet and an outlet, a plurality of passages defined in the lower section, the processing channel being in fluid communication with a reservoir of processing solution via the passages, and pumping means for pumping the processing solution through the passages and the channel, wherein the pumping means is configured such that the processing solution enters the channel via the passages nearest to the inlet and outlet of the channel and exits the channel via the other passage, thereby pulling the material down to a fixed position against the surface wall of the channel and ensuring that substantially no air enters the passage through which the solution exits the channel.
Preferably the surface of the wall of the channel is textured. This achieves good agitation of the flow.
The apparatus and method of the invention prevents the drawing of air into the processing system and thus prevents the oxidation of the solution. By reversing the flow of solution overflow of the system is eliminated should the pump inlet be blocked.
By having the suction return from the lowest part of the processing channel the film is pulled downwards and becomes fixed with respect to the flow of solution. Uniform sensitometry is thus achieved.
The suction of the pump holds the film against the outlet to the pump at a constant predetermined distance. This raises the agitation of the solution by making use of the channeling properties of the surface pattern.
Good agitation of the solution over the film surface is achieved by wiping action over the textured surface of the processing module and the high velocity of the solution through the surface pattern. The textured surface allows free flow of solution over the sensitized surface of the material.
The invention can accommodate any process for color film, color paper, reversal film, reversal paper, black and white film or paper.